Advances in Optical and Photonic Devices 2011 Part 11 pptx

Additionally, it is expected that the QD photonic devices such as a semiconductor laser fabricated on the GaAs wafer will become a powerful candidate to realize an ultra-broadband 1- to

Quantum Dot Photonic Devices and Their Material Fabrications 239 1042.71 nm–ch.4: 1043.85 nm) Each of the central wavelengths is selected for the 100-GHz channel spacing of the AWG by using the discrete single-mode selection method of the QD-CML Figure 9(b) shows a typical eye diagram at ch 2 after transmission A clear eye opening at 12.5 Gbps is observed after the transmission Therefore, the 1-μm waveband with

a 12.5-Gbps transmission over a long-distance (1.5 km) single-mode HF is successfully

YDFA

LN Modulator

1-µm-waveband single-mode holey-fiber Distance: 1.48 km

YDFA 0.6-nm

Communications analyzer

12.5-Gbps

0 dBm

Fig 8 Experimental set-up for testing the 1-μm WDM photonic transport system A 1-μm waveband and single-mode selected quantum dot optical-frequency comb laser (QD-CML) was used for the light source

* Arrayed-Waveguide Grating (AWG)

for 1-micron waveband, 100 GHz spacing

* Injection seeded Sb-based QD FP-LD

Ch4 Ch3 Ch2 Ch1

Wavelength (nm)

After 1.5 km transmission

20 ps/div 1043.2 nm (Ch2)

After 1.5 km transmission

20 ps/div 1043.2 nm (Ch2)

(b) (a)

Fig 9 (a) Optical spectrum of 12.5-Gbps and single-mode selected QD-CML after 1.5-km transmission of the holey fiber (b) Eye opening of ch.2 after transmission

achieved at four different wavelengths by using a wavelength-tunable discrete single-mode selected QD laser device The 1-μm waveband AWG, YDFAs, and other passive devices are also important to construct the 1-μm waveband photonic transport system From these results, a 12.5-Gbps-based WDM photonic transmission with a 100-GHz channel spacing can

be realized in the 1-μm waveband by using the proposed methods Additionally, it is expected that the QD photonic devices such as a semiconductor laser fabricated on the GaAs wafer will become a powerful candidate to realize an ultra-broadband 1- to 1.3-μm photonic transport system

3 Quantum dot structure for advanced photonic devices

In this section, novel material systems of a QD structure are introduced for advanced photonic devices The novel materials of the QD are expected to be used in laser device fabrication, silicon photonics, visible light-emitting devices, etc

3.1 Long-wavelength quantum dot structure

Sb-based III-V semiconductor materials have very narrow-band gap properties Therefore, the use of Sb-based III-V semiconductor QD structures (the Sb atoms are included in the QD structure) are expected for producing long-wavelength-emitting devices (Yamamoto et al

2005 & 2006b) In this section, the Sb-based QD structure fabricated on a GaAs substrate is introduced However, the fabrication of the Sb-based QD such as an InGaSb QD is difficult under conventional QD growth conditions with the MBE method To form the high-quality Sb-based QD structure, a Si atom irradiation technique is proposed as one of the methods for surface treatment Figure 10(a) shows a schematic image of the Si atom irradiation

GaAs

GaAs GaAs

GaAs

Reducing surface free energy :σs

Enhanced S-K growth mode:σs<σf

(σf: Film free-energy)

High-density Sb-based QD structure

Silicon atom irradiation technique

Quantum Dot Photonic Devices and Their Material Fabrications 241 technique Low density Si atoms are irradiated on to the GaAs surface immediately before the Sb-based QD structure growth It is expected that the surface free-energy may be reduced with the irradiation of Si atoms Therefore, the density of the Sb-based QD structure

is enhanced by using this atom-irradiation technique Figures 10(b) and (c) show the AFM images of the Sb-based QD structure without and with the Si atom irradiation, respectively

It is found that the QD density with Si atoms is approximately 100 times higher than that without Si atoms Generally, the QD density as high as 1010/cm2 is necessary if the QD structure is used for developing a laser or other photonic devices Therefore, the optimization of the QD growth conditions such as growth-rate, As-flux intensity, and temperature is also important to obtain the high-quality QD structure Figure 11(a) shows an AFM image of the Sb-based QD/GaAs structure under the optimized growth conditions The height, dimension, and density of the Sb-based QD are approximately 7.5 nm, 25 nm, and 2 × 1010/cm2, respectively

An ultra-wideband emission between wavelengths of 1.08- and 1.48-μm can be successfully realized by using the Sb-based QD/GaAs structure, as shown in Fig 11(b) The long-wavelength and ultra-broadband emission is also obtained from a light-emitting diode (LED) that contained the Sb-based QD in active regions From this result, it is expected that ultra-broadband wavelength (>350 nm) light sources may be achieved with the QD structure for the O-, E-, S-, and C-band (Yamamoto et al 2009a)

Ultra-wideband

InGaSb QDs with Si atom irradiation technique

at Room temperature

Wavelength (nm)

(b) (a)

Fig 11 (a) Atomic force microscope image of high-quality Sb-based QD (InGaSb QD)

structure on GaAs surface (b) Ultra broadband and long-wavelength emission from the based QD/GaAs structure

Sb-The combination of a micro-cavity structure and the QD structure is a very interesting device structure for the investigation of cavity quantum-electrodynamics (QED) Study on the QED of the QD structure is important for constructing a quantum communications system (Ishi-Hayase et al 2007 & Kujiraoka et al 2009) A vertical cavity structure and a photonic crystal structure as an optical resonator are useful for confining the photons (Nomura et al 2009) Figure 12(a) presents a cross-sectional image of a fabricated vertical

cavity structure, which include the Sb-based QD in the cavity A high-performance diffractive Bragg reflector (DBR) for accomplishing the vertical cavity structure can be simply produced by using an AlGaAs material system From the Sb-based QD structure in the vertical cavity, a 1.55-μm sharp emission peak, as shown in Fig 12(b), is successfully observed under the optically pumped condition (Yamamoto et al 2006a) It is also found that a long-wavelength emission with a 1.52-μm peak can be obtained from the similar QD

in the cavity structure at room temperature with a current injection Therefore, it is expected that the use of the long wavelength QD active media in the semiconductor micro-cavity structure is a very useful and important way for fabricating long-wavelength and multiwavelength vertical cavity surface emitting lasers (VCSELs), resonant cavity light-emitting diodes (RCLEDs), single photon sources, etc

n- doped　 GaAs/AlGaAs DBR mirrors

p- doped　 GaAs/AlGaAs DBR mirrors

Cross-sectional image of vertical cavity structure

Stacked InGaSb QDs active layer

Sb-based Quantum Dot

Fig 12 (a) Sb-based QD in micro cavity structure and (b) 1.55-μm wavelength emission spectrum from optically pumped vertical cavity structure

3.2 Quantum dot and related materials for silicon photonics

Silicon photonics technology has been conventionally used to fabricate high performance photonic circuits, which have low-power-consumption, are compact, and are relatively inexpensive to fabricate (Liu et al 2004 & Yamamoto et al 2007b) Poly-, amorphous-, and crystalline-Si waveguide devices have been developed and their properties have been investigated An optical gain region must be provided for silicon waveguide structures to enable the fabrication of active devices such as light emitters and optical amplifiers on silicon platforms (Balakrishnan et al 2006) As one of the candidates of the optical gain media, a III-V semiconductor QD structure on a Si wafer has been investigated Figure 13 shows the schematic image of the Sb-based QD/Si structure and AFM images of the Sb-based QD structures grown between 400°C and 450°C on Si substrates (Yamamoto et al 2007a) From the AFM image, it is found that the high-quality and high-density Sb-based

QD structure can be obtained under the optimal growth conditions by MBE Therefore, a

Quantum Dot Photonic Devices and Their Material Fabrications 243 high-density (>1010 /cm2) and small-sized (<10 nm) QD structure can be obtained by growing the QDs below 400°C From this result, it is expected that the nanostructured Sb-based semiconductors with a low-temperature process (<400°C) should become useful materials for complementary metal oxide semiconductor (CMOS) devices compatible with silicon photonics technology (Yamamoto et al 2008a) Additionally, it is also expected that the nanostructured Sb-based semiconductor will be used for high-speed electro-devices, because the III-Sb compound semiconductor has high-mobility characteristics (Ashley et al., 2007)

et al 1990) An anodization method and a photochemical etching method of a Si wafer are proposed for producing the Si nanoparticles (Yamamoto et al 2001 & Hadjersi et al 2004) It

is known that the Si nanoparticle exhibits a bright visible light emission of red or blue color, and it is considered that this light emission is caused by the quantum size effect of the Si-

QD Figure 14(a) shows a visible emission spectrum from the photochemically etched layers, such as Si nanoparticles (Yamamoto et al 1999) In addition, electroluminescence devices on

a Si wafer are also demonstrated using Si nanoparticles, as shown in Figure 14(b) It is expected that the Si nanoparticle as the Si-QD structure will become a useful material for the visible light-emitting devices with Si-based electric devices (Yamamoto et al 2000)

4 Conclusion

The quantum dot (QD) structures are intensively investigated as the three-dimensional carrier confined structure It is expected that the QD structure can act likely as an atom, which has a controllable characteristic of energy levels The semiconductor QD structure is a very important material for developing novel photonic devices In this chapter, fabrication techniques and characteristics of novel QD photonic devices such as a broadband QD light

500 600 700 800

Area-B Area-A

Area-B Area-A

Light emitting device

by using photo-chemically etched Si

Fig 14 (a) Emission spectra of photochemically etched layers as Si nanoparticles The

emission colors in areas A and B are observed as yellow and red, respectively Each layer is formed on the same Si substrate using a selective area formation technique (b) Visible electroluminescence devices on Si wafer by using the Si-particle as the Si-QD

source and a wavelength tunable QD laser were explained The QD light source act in a broad wavelength band between 1-μm and 1.3-μm can be fabricated on the GaAs substrate

as a low cost and large-sized wafer by using InAs QD and InGaAs QD structures as an active media In addition, a fabrication technique of the Sb-based QD structures on the GaAs substrate was demonstrated for the ultra-broadband light source between 1 and 1.55 μm, and the novel photonic devices using the cavity-QED In other words, by using the QD structure, ultra-broadband optical gain media can be achieved for broadband light-emitting diodes, wavelength tunable laser diodes, semiconductor optical amplifiers, etc Additionally, the QD structures have interesting opto-electric characteristics compared to the conventional quantum well and bulk materials It is expected that the QD optical frequency comb laser (QD-CML) can be realized by using the useful characteristics of the

QD structure

Ultra-broadband optical frequency resources in the short wavelength band such as the 1-μm waveband can be used for optical communications As the 1-μm waveband photonic transport system, over 10 Gbps and a long distance transmission were successfully demonstrated by using high-performance key components such as single-mode QD light sources, long-distance holey fibers, and YDFAs Therefore, it is expected that the uses of the

QD photonic devices enhance the usable waveband for optical communications

For the silicon photonics, a fabrication technique for the high-quality Sb-based QD structure

on a Si wafer was demonstrated clearly As the other QD structure for the silicon photonics,

it is also demonstrated that Si nanoparticles as the Si-QD become candidates for the emitting devices on the Si wafer

light-It is expected that a fabrication and application of the QD structure will provide a breakthrough technology for the creation of novel photonic devices, improvement in the

Quantum Dot Photonic Devices and Their Material Fabrications 245 existing photonic devices, and enhancement of usable optical frequency resources in the all-photonic waveband

5 Acknowledgments

The authors would like to thank Prof H Yokoyama at New Industry Creation Hatchery Center (NICHe) of Tohoku University, Prof H Takai at Tokyo Denki University (TDU), Drs

K Akahane, R Katouf, T Kawanishi, I Hosako, and Y Matsushima at the National Institute

of Information and Communications Technology (NICT) for discussing novel technologies

of the quantum dot photonic devices and lasers The authors are deeply grateful to Drs K Mukasa, K Imamura, R Miyabe, T Yagi, and S Ozawa at FURUKAWA ELECTRIC CO for discussing broadband transmission lines of the novel optical fibers

6 References

Akahane, K.; Yamamoto, N., Sotobayashi, H & Tsuchiya, M (2008) 1.7-μm Laser Emission

at Room Temperature using Highly-Stacked InAs Quantum dots Proceedings of Indium Phosphide and Related Material (IPRM) 2008, Versailles, 171

Arakawa, Y & Sakaki, H (1982) Multidimensional quantum well laser and temperature

dependence of its threshold current Appl Phys Lett Vol 40, 939 (1982) 939

Ashley, T.; Buckle, L.; Datta, S.; Emeny, M T.; Hayes, D G.; Hilton, K P.; Jefferies, R.;

Martin, T.; Phillips, T J.; Wallis, D J.; Wilding, P J & Chau, R (2007) Heterogeneous InSb quantum well transistors on silicon for ultra-high speed, low

power logic applications Electron Lett., Vol 43, (2007) 777

Balakrishnan, G.; Jallipalli, A.; Rotella, P.; Huang, S.; Khoshakhlagh, A.; Amtout, A &

Krishna, S (2006) Room-Temperature Optically Pumped (Al)GaSb Vertical-Cavity

Surface-Emitting Laser Monolithically Grown on an Si(100) Substrate IEEE J Sel

Topics in Quantum Electron, Vol 12, (2006) 1636

Canham, L.T (1990) Silicon quantum wire array fabrication by electrochemical and

chemical dissolution of wafers Appl Phys Lett Vol 57, (1990) 1046

Gnauck, A H.; Charlet, G.; Tran, P.; Winzer, P.; Doerr, C.; Centanni, J.; Burrows, E.;

Kawanishi, T.; Sakamoto, T & Higuma, K (2007) 25.6-Tb/s C+L-Band

Transmission of Polarization-Multiplexed RZ-DQPSK Signals, Proceedings of

OFC2007, 2007, Anaheim, CA, PDP19

Gubenko, A.; Krestnikov, I.; Livshtis, D.; Mikhrin, S.; Kovsh, A.; West, L.; Bornholdt, C.;

Grote, N & Zhukov, A (2007) Error-free 10 Gbit/s transmission using individual

Fabry-Perot modes of low-noise quantum-dot laser Electron Lett., Vol 43, (2007)

1430

Hasegawa, H.; Oikawa, Y.; Yoshida, M.; Hirooka, T & Nakazawa, M (2006) 10Gb/s

transmission over 5 km at 850nm using mode photonic crystal fiber,

single-mode VCSEL, and Si-APD IEICE Electron Express, Vol 3, (2006) 109-114

Hadjersi, T.; Gabouze, N.; Yamamoto, N.; Sakamaki, K & Takai, H (2004)

Photoluminescence from photochemically etched highly resistive silicon Thin solid

films, Vol 459, (2004) 249-253

Ishi-Hayase, J.; Akahane, K.; Yamamoto, N.; Sasaki, M.; Kujiraoka, M & Ema, K (2007)

Radiatively limited dephasing of quantum dot excitons in the telecommunications

wavelength range Appl Phys Lett., Vol 91 (2007) 103111

Katouf, R.; Yamamoto, N.; Akahane, K.; Kawanishi, T & Sotobayashi, H (2009) 1-µm- band

transmission by use of a wavelength tunable quantum-dot laser over a

hole-assisted fiber, Proceedings of SPIE 7234, p 72340G, 2009

Koyama, F.; (2009) VCSEL photonics –advances and new challenges- IEICE Electronics

Express, Vol 6 (2009) 651

Kujiraoka, M.; Ishi-Hayase, J.; Akahane, K.; Yamamoto, N.; Ema, K & Sasaki, M (2009)

Ensemble effect on Rabi oscillations of excitons in quantum dots Phys Stat Sol A

Applications and Materials Science, Vol 206 (2009) 952

Ledentsov, N.N.; Kovsh, A.R.; Zhukov, A.E.; Maleev, N.A.; Mikhrin, S.S.; Vasil'ev, A.P.;

Semenova, E.S.; Maximov, M.V.; Shernyakov, Yu.M.; Kryzhanovskaya, N.V.; Ustinov, V.M.; Bimberg, D (2003) High performance quantum dot lasers on GaAs

substrates operating in 1.5 μm range Electron Lett., Vol 39 (2003) 1126

Liu, A.; Jones, R.; Liao, L.; Rubio, D.S.; Rubin, D.; Cohen, O.; Nicolaescu, R & Paniccia, M

(2004) A high-speed silicon optical modulator based on a metal–oxide–

semiconductor capacitor Nature, Vol 427, (2004) 615

Liu, H Y.; Hopkinson, M.; Harrison, C N.; Steer M J & Frith R (2003) Optimizing the

growth of 1.3 μm InAs/InGaAs dots-in-a-well structure Jpn J Appl Phys., Vol 93

(2003) 2931

Mukasa, K.; Miyabe, R.; Imamura, K.; Aiso, K.; Sugizaki, R & Yagi, T (2007) Hole assisted

fibers (HAFs) and holey fibers (HFs) for short-wavelength applications, Proceedings

of SPIE 6779, p 67790J-1, 2007

Mukasa, K.; Imamura, K.; Sugizaki, R & Yagi, T (2008) Comparisons of merits on

wide-band transmission systems between using extremely improved solid SMFs with Aeff of 160mm2 and loss of 0.175dB/km and using large-Aeff holey fibers enabling

transmission over 600nm bandwidth Proceedings of OFC 2008, San Diego, OThR1

Nomura, M.; Iwamoto, S., Tandaechanurat, A.; Ota, Y.; Kumagai, N & Arakawa Y (2009)

Photonic band-edge micro lasers with quantum dot gain Optics Express, Vol 17

(2009) 640

Otsubo, K.; Hatori, N.; Ishida, M.; Okumura, S.; Akiyama, T.; Nakata, Y.; Ebe, H.; Sugawara,

M & Arakawa, Y (2004) Temperature-Insensitive Eye-Opening under 10-Gb/s Modulation of 1.3-µm P-Doped Quantum-Dot Lasers without Current

Adjustments Jpn J Appl Phys., Vol 43, (2004) L1124

Paschotta, R.; Nilsson, J.; Tropper, A.C & Hanna, D.C (1997) Ytterbiumdoped fiber

amplifiers IEEE J Quantum Electron, Vol 33, (1997) 1049–1056

Rafailov, E.U.; Cataluna, M.A & Sibbett, W (2007) Mode-locked quantum-dot lasers Nature

photonics, Vol 1, (2007) 395

Shimizu, H.; Saravanan, S.; Yoshida, J.; Ibe, S.; & Yokouchi N (2007) Long-Wavelength

Multilayered InAs Quantum Dot Lasers Jpn J Appl Phys., Vol 46 (2007) 638 Sotobayashi, H.; Chujo, W.; Konishi, A & Ozeki, T (2002) Wavelength-band generation and

transmission of 3.24-Tbit/s (81-channel WDM×40-Gbit/s) carrier-suppressed return-to-zero format by use of a single supercontinuum source for frequency

standardization J Opt Soc Am B, Vol 19 (2002) 2803

Tanguy, Y.; Muszalski, J.; Houlihan, J.; Huyet, G.; Pearce, E J.; Smowton, P.M & Hopkinson,

M (2004) Mode formation in broad area quantum dot lasers at 1060 nm Opt

Comm Vol 235, (2004) 387-393

Quantum Dot Photonic Devices and Their Material Fabrications 247 Tanaka, Y.; Ishida, M.; Maeda, Y.; Akiyama, T.; Yamamoto, T.; Song, H.; Yamaguchi, M.;

Nakata, Y.; Nishi, K Sugawara, M & Arakawa Y (2009) High-Speed and Temperature-Insensitive Operation in 1.3-μm InAs/GaAs High-Density Quantum

Dot Lasers Proceedings of OFC 2009, San Diego, OWJ1

Yokoyama, H.; Sato, A.; Guo, H.-C.; Sato, K.; Mure, M & Tsubokawa, H (2008)

Nonlinear-microscopy optical-pulse sources based on mode-locked semiconductor lasers Opt

Express, Vol 16, No 22, (2008) 17752

Yamamoto, N & Takai, H (1999) Blue Luminescence from Photochemically Etched Silicon

Jpn J Appl Phys., Vol 38, (1999) 5706-5709

Yamamoto, N.; Sumiya A & Takai, H (2000) Electroluminescence From Photo-chemically

Etched Silicon Materials Science & Engineering B69-70, (2000) 205-209

Yamamoto, N & Takai, H (2001) Formation mechanism of silicon based luminescence

material using a photo chemically etching method Thin solid films, Vol 388, (2001)

138-142

Yamamoto, N.; Akahane, K.; Gozu, S & Ohtani, N (2005) Over 1.3 µm continuous-wave

laser emission from InGaSb quantum-dot laser diode fabricated on GaAs

substrates Appl Phys Lett., Vol 86, (2005) 203118

Yamamoto, N.; Akahane, K.; Gozu, S.; Ueta, A & Ohtani, N (2006a) 1.55-μm-Waveband

Emissions from Sb-Based Quantum-Dot Vertical-Cavity Surface-Emitting Laser

Structures Fabricated on GaAs Substrate Jpn J Appl Phys., Vol 45, (2006)

3423-3426

Yamamoto, N.; Akahanea, K.; Gozu, S.; Ueta, A.; Ohtani, N & Tsuchiya, M (2006b)

Sb-based quantum dots for creating novel light-emitting devices for optical

communications, Proceedings of SPIE 6393, p 63930A 2006

Yamamoto, N.; Akahanea, K.; Gozu, S.; Ueta, A.; Ohtani, N & Tsuchiya, M (2007a) Growth

of InGaSb quantum dot structures on GaAs and Silicon substrates Jpn J Appl

Phys., Vol 46, (2007b) 2401-2404

Yamamoto, N.; Akahane, K.; Nakamura, Y.; Naka, Y.; Kishi, M.; Sugawara, H.; Kawanishi,

T & Tsuchiya, M (2007b) Silicon-based photonic network devices and materials,

Proceedings of SPIE, Vol.6775, (2007) 67750O

Yamamoto, N.; Akahane, K.; Gozu, S.; Ueta, A & Tsuchiya, M (2008a) Low-temperature

growth of nanostructured InGaSb semiconductors on silicon substrates Physica E,

Vol 40, No 6, (2008) 2195-2197

Yamamoto, N.; Akahane, K.; Sotobayashi, H & Tsuchiya, M (2008b) O-band InAs quantum

dot (QD) laser diode with Sb-molecule sprayed Dot-in-Well (DWELL) structures

fabricated on GaAs substrates, Proceedings of OECC2008, 2008, Sydney, Australia,

TuH3

Yamamoto, N.; Sotobayashi, H.; Akahane, K & Tsuchiya, M (2008c) Quantum-dot

Fabry-Perot laser-diode with a 4-THz injection-seeding bandwidth for 1-μm

optical-waveband WDM systems, Proceedings of ISLC2008, p 20, 2008, Sorrento, Italy

Yamamoto, N.; Sotobayashi, H.; Akahane, K.; Tsuchiya, M.; Takashima, K & Yokoyama, H

(2008d) 10-Gbps, 1-μm waveband photonic transmission with a harmonically

mode-locked semiconductor laser Opt Express, Vol 16, No 24, (2008) 19836

Yamamoto, N & Sotobayashi, H (2009a) All-band photonic transport system and its device

technologies Proceedings of SPIE, Vol 7235 (2009) 72350C

Yamamoto, N.; Katouf, R., Akahane, K., Kawanishi, T & Sotobayashi, H (2009b) 1-μm

waveband, 10Gbps transmission with a wavelength tunable single-mode selected

quantum-dot optical frequency comb laser, Proceedings of OFC 2009, San Diego,

OWJ4

Yamamoto, N.; Fujioka, H.; Akahane, K.; Katouf, R.; Kawanishi, T.; Takai, H & Sotobayashi,

H (2009c) O-Band InAs/InGaAs Quantum Dot Laser Diode with Sandwiched

Sub-Nano Separator (SSNS) Structures Proceedings of Conference on Lasers and

Electro-Optics (CLEO), Baltimore, JThE

14

Silicon Photomultiplier - New Era of Photon Detection

Concerning modern semiconductor structures for the photon detection, few options were investigated for the detecting of the low photon flux, but main critical problem to develop the semiconductor device was the relative high level of thermal noise of semiconductor detector structure and associated frontend electronics One of the solutions, overcome this problem is Visible Light Photon Counter (VLPC) (Atac, 1993) This device is semiconductor avalanche structure operated at the temperature of 4K, for the suppression of thermal noise The results was successful - possibility to detect low photon flux up to single photon, but operational conditions are to complicated to be acceptable for wide area application, cryostat for the 4K temperature up to now is challenge even in the laboratory conditions Development of the modern detection structures for the low photon flux Si was initiated at the beginning of 90’th from studies of Silicon Metal Oxide Semiconductor (MOS) structures with avalanche breakdown mode operation for the detecting of single visible light photons [Gasanov et al., 1989] The results were positive, but strong limitation was the necessity to include external recharge circuits for the discharge the detector structure after charging the MOS structure during the photons detection Next step was implementation of special resistive layer instead oxide layers, Metal Resistive Semiconductor (MRS) structures, which gives the possibility to recharge the structure after photon detection and in addition to control the breakdown avalanche process by quenching Such structures had very high and stable amplification characteristics for photons detection, in comparison to conventional avalanche photodetector structures, but limited sensitive area The idea of Silicon Photomultiplier or more precisely Silicon Photoelectron Multipliers was created for overcoming problem of above mentioned structures as small sensitive area due to nonstability of amplification over large area, low dynamic range, improving the resolution

It was decided create the fine metal resistor semiconductor structure with local space

distributed pn-junctions (micro-cells) and common output The result was fascinated, first

time clear single photon spectra was detected on the semiconductor structure at room temperature

Results of study such structures was presented on the 9th European semiconductor conference in 1995 (Saveliev, 1995)

And the first concept of Silicon Photomultiplier was proposed fine silicon structure of avalanche breakdown mode micro-cells with common resistive layer quenching element and common electrodes Results of this development were presented on the conference Beaune 1999 (Saveliev & Golovin, 2000; Bondarenko et al., 2000)

The goals of next steps were the optimization of the detection structures in particular increasing so called geometrical efficiency – ratio of area sensitive to photons to the total area of the silicon photomultiplier i.e getting as much as detection efficiency and tuning the optimal operation condition in term of bias and time performance, and generally improve the technological processes With advanced technology, what became available in the middle of 90th, the micro-cells are positioned as close as possible to each other, the common resistive layer as quenching element was substituted by individual integrated resistors coupled to the individual micro-cells with optimization of position and size And the modern silicon photomultiplier structures start to be available for the applications (Golovin

V & Saveliev V., 2004)

New problem for optimized structures of silicon photomultipliers was the problem of optical crosstalk in fine detection structure due to light emission during the avalanche breakdown processes in Silicon The phenomena of light emission from avalanche breakdown process is well known (A.G.Chynoweth & K.G.McKay, 1956) For the Silicon Photomultipliers with tiny space structure of microcells, the probability of detection secondary photons by neighborhood microcells is quite high and should be taking to account Mainly this problem is affected of area of very low photon flux where the optics crosstalk could significantly change the results

of measurement The solution of this problem was achieved by implementation of modern technology process, physically optical isolation of the micro-cells on the integrated structure level For the suppression of the optical crosstalk between the micro-cells, the trench structure was implemented around micro-cells as optic isolating elements and filled by optic non transparent material The latest development in this area brings the very high performance for very low photon flux and created special type of silicon photomultiplier - quantum photo detectors (QPD) (Saveliev et al., 2008)

Silicon Photomultiplier is first semiconductor detector which could not only compete with photomultiplier tubes in term of detecting of low photon flux, but has a great advantages in performance and operation conditions and has great future in many areas of applications such as experimental physics, nuclear medicine, homeland security, military applications and other Silicon Photomultipliers shows the excellent performance including the single photon response at room temperature (intrinsic gain of multiplication is 106), high detection efficiency ~25-60% for the visible range of light, fast timing response ~30 ps Operational condition are suitable for many applications: operation bias 20-60 V, operated at room temperature as well in cooling conditions, not sensitive to electromagnetic fields Production

on base modern semiconductor technology, compatible with mass production semiconductor technology, compact, typical size of few mm2 and flexible for assembling of the arrays In this publication is impossible to eliminate all aspects of the silicon photomultiplier discovery and mainly will emphasise to more common feature to silicon photomultiplier development

2 Conceptual idea

The main problem of detection of low photon flux or single photon is defined by nature of photons, physics of the photon interaction with matter and processes of converting the results